#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include "./getch/getch.h"

#define MAXWORD 100
#define NKEYS (sizeof keytab / sizeof(struct key))

struct key
{
	char *word;
	int count;
};

struct key keytab[] = {
	{"auto", 0},
	{"break", 0},
	{"case", 0},
	{"char", 0},
	{"const", 0}
	// ..........
};

int getword(char *, int);
struct key *binsearch(char *, struct key *, int);

// count C keywords; pointer version
int main()
{
	struct key *p;
	char word[MAXWORD];

	while(getword(word, MAXWORD) != EOF)
		if(isalpha(word[0]))		// 识别是否是字母
			if((p = binsearch(word, keytab, NKEYS)) != NULL)
				p->count++;
	for(p = keytab; p < keytab + NKEYS; p++)
		if(p->count > 0)
			printf("%4d %s \n", p->count, p->word);

	return 0;
}

// binsearch: find word in tab[0] ... tab[n-1]
struct key *binsearch(char *word, struct key *tab, int n)
{
	int cond;
	struct key * low = &tab[0];
	struct key * high = &tab[n]; 
	struct key * mid;

	while(low < high)
	{
		mid = low + (high - low) / 2;
		if((cond = strcmp(word, mid->word)) < 0)
			high = mid;
		else if(cond > 0)
			low = mid + 1;
		else 
			return mid;
	}
	return NULL;
}

// getword: get next word or character from input
int getword(char *word, int lim)
{
	int c, getch(void);
	void ungetch(int);
	char *w = word;

	while(isspace(c = getch()))		// 识别是否是空白符
		;
	if(c != EOF)
		*w++ = c;
	if(!isalpha(c))				// 识别是否是字母
	{
		*w = '\0';
		return c;
	}
	for(; --lim > 0; w++)
		if(!isalnum(*w = getch()))	// 识别是否是字母和数字
		{
			ungetch(*w);
			break;
		}
	*w = '\0';
	return word[0];
}
